1. Field of the Invention
This invention pertains to insulating materials, and more particularly to insulating materials utilized to reduce heat transfer through the doors and windows of a building.
2. Description of the Prior Art
It has long been recognized that heat transfer through glass doors and windows represents a major portion of total building heat gains and losses. For example, a modern home constructed with the latest energy saving materials and methods was the subject of a recent energy loss study. The window area represented only 19% of the floor area, but the windows accounted for 33% of the total heat loss.
Various insulators have been developed to increase window thermal efficiencies by attacking one or more of the contributors to heat transfer: convection, conduction, radiation, and infiltration. The insulators have frequently taken the form of folding window shades, as for example, the well known Roman shade. In the extended position, the shades generally cover the door or window panes and sashes. In many cases the shade sides, top, and bottom are held more or less firmly against the casings by mechanical means such as weights or springs to form seals against infiltration. U.S. Pat. No. 4,335,774 shows a thermal window barrier having spring retained sides. Pull cords of various designs are commonly employed to aid in raising and lowering the shades, as shown, for example, in U.S. Pat. Nos. 3,777,800 and 3,487,875.
If the insulated window shade is used inside a home, esthetic properties of the shade are an important factor. The insulating material is frequently covered with a decorative material to match the room decor. It is also desirable that shades present a neat appearance when in the raised or folded position. This presents a problem with many types of Roman shades. The materials employed are frequently quite thick, often in the neighborhood of one and one-half inches. Raising a thick Roman shade produces folds in it that are frequently bulky and unsightly. U.S. Pat. No. 3,856,072 illustrates the general shape a bulky insulator may assume in the raised position.
The bulky and looped appearance of raised shades may be greatly improved if the shades are fabricated with rather sharply defined pleats. U.S. Pat. No. 4,317,481 illustrates a window shade composed of slats of thermal insulating material attached to a flexible sheet. The slats are spaced apart vertically a slight distance to allow the flexible sheet to fold sharply between the slats. While this folded shade presents a neat appearance, it is costly to fabricate because it requires two separate materials which must be sewn or otherwise joined together. U.S. Pat. Nos. 3,952,788 and 3,487,875 disclose shades that incorporate small reinforcing plates to provide a neat and pleated appearance in the folded position. The use of separate pieces is undesirable because of their cost and because of the cost of adapting the shade fabric to accommodate the pieces.
Accordingly, a need exists for an insulating window shade that is inexpensive, thermally efficient with respect to conduction, convection, radiation, and infiltration, and that presents a neat pleated appearance when in the folded or raised position.